lowpost

My mechanic installed new xenon assemblies but one of them sits too low. I was told I could adjust (raise) the height by turning the 2 8mm bolt that hold the assembly in place and are accessible from the top. Question is, the bolts are screwed into a circular metal piece with notches, and it's not clear if I'm supposed to turn the bolt or this round metal piece. Anyone know. This is not about lighting adjustment. I know how to do that. This is about how the assembly physically secured. Thanks.